Co掺杂LiFePO_4/C的共沉淀-微波合成及电化学性能

Electrochemical Properties of Co-doped LiFePO_4/C Prepared by Coprecipitation-microwave Method

采用共沉淀-微波法制备了Co掺杂的锂离子电池正极材料LiFe1-xCoxPO4/C(x=0.00、0.01、0.03、0.05、0.07、0.09)。研究了微波时间、柠檬酸量、掺Co量等因素对材料结构、形貌和电性能的影响。XRD、SEM和电化学测试表明:该方法制备的样品为橄榄石型非晶结构,粒径尺寸为0.5～5μm,颗粒分布比较均匀。微波15 min、柠檬酸量为20wt%时,LiFePO4/C电化学性能最优,0.1C倍率放电可达124 mA.h/g,第20次循环的比容量为117 mA.h/g。掺杂Co在很大程度上可以提高LiFePO4/C的电化学性能,当Co含量为5 wt%时,LiFe0.95Co0.05PO4/C的比容量为最大值,0.1C倍率放电可达136 mA.h/g,第20次循环的比容量为125 mA.h/g,容量保持率为91.9%。

Stoichiometric Co-doped lithium iron phosphates LiFe1-xCoxPO4/C （x=0.00, 0.01, 0.03, 0.05, 0.07, 0.09） cathode materials for lithium ion batteries was synthesized by coprecipitation-microwave method. The effects of microwave time, the amount of citric acid, the content of doped cobalt on the microstructure, morphology and electrochemical properties of LiFe1-xCoxPO4/C were analyzed. The results show that the optimal condition is： microwave time of 15 min, the amount of citric acid reaches 20wt%. Under this condition, the sample has an olivine-type amorphous structure and grain size is in the range from 0.5μm to 5 p.m. When charge-discharge at 0.1C, its initial specific discharge capacity is 124 mA.h/g, the specific capacity at the 20th cycle is 117 mA .h/g. The content of Co is an important factor to influence the performance of LiFePO4. Charge-discharge test shows that the cathode materials with the Co content of 5wt% possess excellent charge/discharge capacities, about 136 mA. h/g at 0.1 C rate and 125 mA. h/g in the 20th cycle, the capacity retention is 91.9%.